Geology Reference
In-Depth Information
rutile and titanium rich slag as generated by the metallurgical treatment of the
ilmenite ore. Here the TiCl
4
, a fuming colourless and transparent liquid, is then
reduced in a special stainless steel vessel with molten magnesium in an argon at-
mosphere at 850-900
o
C. It is also condensed and separated by fractional distillation
to a purity of at least 99.9%. This is a batch process where pure magnesium is
first melted before controlled amounts of TiCl
4
are added to the mix, since the
reaction is highly exothermic. A titanium sponge is obtained and magnesium chlo-
ride is extracted at regular intervals by an application of pressure. The remaining
magnesium and magnesium tetrachloride is extracted by high temperature vacuum
at around 1000
o
C during 30-60 hours, leaving a purer titanium sponge. The mag-
nesium chloride is then further electrolysed, obtaining magnesium metal that is
further used as a reducing agent, and chlorine that is itself reused in the chlorina-
tion process (Kawatra, 2011). The titanium sponge and eventually titanium scrap
is conducted in a vacuum arc re-melting furnace. First, titanium is compacted in
blocks using a press and shaped to form electrodes. These blocks then melt in vac-
uum conditions under the arc formed between the electrodes and the bottom of the
water-cooled copper crucible. As the electrode melts, the metal moves downside
the furnace where molten titanium is collected forming ingots. These ingots are
converted into blooms by breakdown forging and become ready for machining on
market demand
17
.
The production of ferrotitanium meanwhile, is much simpler since no uncon-
ventional operations are needed. For producing ferrotitanium, it is advantageous
to start with ilmenite as the primary ore. The reduction is a conventional metal-
lothermic process undertaken in a refractory lined crucible or in an electric furnace.
Additionally, ferrotitanium can be produced by melting titanium swarf and iron
scrap which has been previously reduced in size via oxy-flame cutting, then chipped
and cleaned to remove any potential oil and moisture being introduced into the
induction melting furnace. The titanium swarf is degreased in a rotary dryer where
gases pass through an afterburner and are partially recirculated. The off-gases then
flow through a ceramic filter and are neutralised with sodium bicarbonate prior to
sending them to the stack. As the furnace operates in batch, the ferrotitanium
composition is controlled by the frequent weighing of any changes and a product
analysis. Once the ferrotitanium is completely melted, it is tapped off into ingot
moulds (IPPC, 2009). Fig. 8.11 is a schematic of the processes for ferro-titanium
production.
Norgate et al. (2007) obtain a life cycle gross energy requirement for the Kroll
refining process of 361 GJ/t Ti. They also state a GWP of the process of 35.7
tCO
2
e=t Ti. Additionally, Bravard et al. (1972) published the following data
on producing titanium oxide from ilmenite: 23 GJ/t of titanium for its mining and
concentration and 687 GJ/t in the refining. Yoshiki-Gravelsins et al. (1993), indicate
that refining requires 406.8 GJ/t, which is similar to Batelle-Columbus-Laboratories
(1975)'s 430 GJ/t.
17
See http : ==www:osakati:co:jp=e=e
p
roduct=titan=index:html. Accessed Sep. 2011.
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